Citizens band radio receivers have become increasingly popular for use in automobiles and trucks, sometimes to provide radio communication for volunteer firemen, or to enable radio communication between licensed citizens band broadcasters, and for various other purposes. Usually, the citizens band radio messages come in intermittently and irregularly, and many users prefer to listen to AM radio or FM radio broadcasts or to an audio tape player during the intervals when the CB radio receiver is silent.
It has been proposed heretofore to provide a combined CB radio receiver and AM or FM radio receiver for use in a car or truck with a switching arrangement for enabling the AM or FM receiver to play except when an incoming message is being received by the CB receiver. Such a combination assembly is relatively expensive and does not suit the needs of a user who simply wants to add on a CB receiver to an AM, FM or AM/FM receiver or a tape player already installed in the vehicle, or to provide an automatic switching interconnection between an existing CB receiver and an existing AM, FM or AM/FM receiver or tape player in the vehicle.